Reversibly deployable spoiler

ABSTRACT

A reversibly deployable spoiler for a vehicle comprises a body and an active material in operative communication with the body. The active material, such as shape memory material, is operative to change at least one attribute in response to an activation signal. The active material can change its shape, dimensions and/or stiffness producing a change in at least one feature of the active spoiler airflow control device such as shape, dimension, location, orientation, and/or stiffness to control vehicle airflow and downforce to better suit changes in driving conditions such as speed, while reducing maintenance and the level of failure modes. An activation device, controller and sensors may be employed to further control the change in at least one feature of the active spoiler airflow control device such as shape, dimension, location, orientation, and/or stiffness. A method for controlling vehicle airflow selectively introduces an activation signal to initiate a change of at least one feature of the device that can be reversed upon discontinuation of the activation signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application relates to and claims the benefit of priority to U.S.Provisional Patent Application No. 60/719,375 filed on Sep. 22, 2005,incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to airflow control devices for vehicles,and more particularly, to reversibly deployable vehicle spoilers thatuse active materials to effect deployment and retraction.

Airflow over, under, around, and/or through a vehicle can affect manyaspects of vehicle performance including vehicle drag, vehicle lift anddown force, and cooling/heat exchange for a vehicle powertrain and airconditioning systems. Reductions in vehicle drag improve fuel economy.Vehicle lift and downforce can affect vehicle stability and handling. Asused herein, the term “airflow” refers to the motion of air around andthrough parts of a vehicle relative to either the exterior surface ofthe vehicle or surfaces of elements of the vehicle along which exteriorairflow can be directed such as surfaces in the engine compartment. Theterm “drag” refers to the resistance caused by friction in a directionopposite that of the motion of the center of gravity for a moving bodyin a fluid. The term “lift” as used herein refers to the component ofthe total force due to airflow relative to a vehicle acting on thevehicle in a vertically upwards direction. The term “downforce” usedherein refers to the component of total force due to airflow relative tothe vehicle acting on a vehicle in a vertically downward direction.

Devices known in the art of vehicle manufacture to control airflowrelative to a vehicle are generally of a predetermined, non-adjustablegeometry, location, orientation and stiffness. Such devices generally donot adapt as driving conditions change, thus the airflow relative to thevehicle cannot be adjusted to better suit the changing drivingconditions. Additionally, current under-vehicle airflow control devicescan reduce ground clearance. Vehicle designers are faced with thechallenge of controlling the airflow while maintaining sufficient groundclearance to avoid contact with and damage by parking ramps, parkingblocks, potholes, curbs and the like. Further, inclement weather, suchas deep snow slush or rainfall, can damage the device and/or impairvehicle handing.

There are many general types of airflow control devices used forvehicles. One of these is spoilers. FIG. 1 illustrates a vehicle 1 thatincludes a spoiler 5 in the location typically associated with itsfunction as discussed below. A spoiler is designed to improve tractionby increasing the downward force on the rear portion of a vehicle. Theuse of spoilers increases the cornering capability and improvesstability at high speeds, but often at the expense of additionalaerodynamic drag and weight. Without the presence of a spoiler, the areaat the rear of the vehicle would experience more lift at higher speedsas a function of the flow aerodynamics.

Current spoilers are generally of a fixed geometry, location,orientation, and stiffness. Such devices can thus not be relocated,reoriented, reshaped, etc. as driving conditions change and thus airflowover/around the vehicle body can not be adjusted to better suit thechanged driving condition. In those spoilers that are not of a fixedgeometry, location, etc., the spoilers are typically made adjustable bymounting and/or connecting the devices to hydraulic, mechanical,electrical actuators and/or the like. For example, some vehicle spoilersmay adjust location and/or orientation in response to an actuatorsignal. However, such actuators generally require additional componentssuch as pistons, motors, solenoids and/or like mechanisms foractivation, which increase the complexity of the device often resultingin increased failure modes, maintenance, and manufacturing costs.

Accordingly, it would be desirable to have a deployable spoiler that canbe tuned according to the driving conditions and that enhances devicesimplicity while reducing device problems and the number of failuremodes.

BRIEF SUMMARY

Reversibly deployable spoilers and methods are disclosed herein. In oneembodiment, the spoiler defines a surface of the vehicle that canincrease or decrease airflow down force during movement of the vehicle.The spoiler comprises a housing having an opening; an airflow controlmember translatably disposed within the housing and slidably engagedwith the opening; and an active material actuator comprising an activematerial in operative communication with the airflow control member toeffect deployment and retraction of the airflow control member from andinto the housing.

In another embodiment, the spoiler comprises a housing comprising anairflow control member rotatably disposed within the housing, whereinrotation of the airflow control member increases or decreases airflowdown force during movement of the vehicle; and an active materialactuator in operative communication with the airflow control member toeffect rotation of the airflow control member.

In yet another embodiment, a spoiler for a vehicle comprises a posttranslatable to a vehicle surface; an airflow control member mounted onthe post; and an active material actuator comprising an active materialin operative communication with the post to effect translation of thepost relative to the vehicle surface.

In still another embodiment, the spoiler comprises a flexible surfacepositioned on the vehicle so as to affect airflow down force uponflexure thereof; a rotatable cam in contact with the flexible surface;and an active material actuator in operative communication with theairflow control member to effect rotation of the cam and cause flexureto the flexible surface.

The above described and other features are exemplified by the followingfigures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures, which are exemplary embodiments andwherein like elements are numbered alike:

FIG. 1 illustrates a vehicle that includes a spoiler in a locationtypically associated with its function;

FIG. 2 illustrates a sectional view of a reversibly deployable spoilerfor a vehicle in a retracted position in accordance with one embodimentof the present disclosure;

FIG. 3 illustrates a sectional view of the reversibly deployable spoilerof FIG. 2 in a deployed position;

FIG. 4 illustrates a sectional view of a reversibly deployable spoilerfor a vehicle in a deployed position in accordance with anotherembodiment of the present disclosure;

FIG. 5 illustrates a sectional view of the reversibly deployable spoilerof FIG. 4 in a retracted position;

FIG. 6 illustrates a sectional view of a reversibly deployable spoilerfor a vehicle in a retracted position in accordance with yet anotherembodiment of the present disclosure;

FIG. 7 illustrates a sectional view of the reversibly deployable spoilerof FIG. 6 in a deployed position;

FIG. 8 illustrates a sectional view of a reversibly deployable spoilerthat employs a rotary mechanism in accordance with another embodiment;

FIG. 9 illustrates a sectional view of a reversibly deployable spoilerthat employs a rotary mechanism in accordance with yet anotherembodiment;

FIG. 10 illustrates a perspective view of a reversibly deployablespoiler that utilizes active material translatable posts in accordancewith another embodiment;

FIG. 11 is a sectional view of the reversibly deployable spoiler of FIG.10;

FIG. 12 illustrates a suitable active material actuator for retractingthe spoiler of FIG. 10; and

FIG. 13 illustrates a suitable active material actuator for deployingthe spoiler of FIG. 10.

DETAILED DESCRIPTION

Active material actuated reversibly deployable airflow spoilers aredisclosed herein. The airflow spoilers are suitable for use on vehicleson which it might be desirable to have on-demand greater downforce suchas may be desired for vehicles utilized on occasion in competitivedriving. It should be apparent that the airflow spoilers are mounted ona surface of the vehicle that can affect downforce to the vehicle duringdriving conditions. Typically, this position is at or about a rear deckof the vehicle although it is not intended to be limited to suchlocation. Either deployment or stowing of the spoiler in theseembodiments is in each case based on either a rigid body translation orrotation effected through just a single activation cycle (or at most avery small number of activation cycles) of an active material.Advantages associated with utilizing active materials to effect thesechanges include, among others, increased device simplicity, a reducednumber of failure modes and thus increased device robustness, andreduced device volumes, masses, and energy requirements for activationbecause of their higher energy densities.

The classes of active materials included are those that exhibit a changein stiffness and/or dimensions in response to an actuation signal whichcan take various forms depending on the particular active material.Suitable active materials include, but are not limited to, shape memoryalloys (SMA), shape memory polymers (SMP), electroactive polymers (EAP),ferromagnetic SMAs, electrorheological fluids (ER), magnetorheologicalfluids (MR), piezoelectric ceramics, various combinations of theforegoing materials, and the like such as is disclosed in pending U.S.patent application Ser. Nos. 10/983,330, 10/893,119, 10/872,327, and10/983,329, all of which are incorporated by reference in theirentireties.

The active material based spoiler devices for controlling vehicleairflow are generally directed to devices in which the active material(one or more) is connected externally either directly or remotely to asurface of an airflow control member causing either rigid bodytranslation, rotation, or morphing of the airflow control device'sairflow control surfaces.

In an embodiment shown in FIGS. 2 and 3, there is shown a spoilergenerally designated by reference numeral 10 in the retracted anddeployed positions, respectively. The spoiler 10 includes a housing 12that contains an active material based actuator 14 and a deployableairflow member 16. The housing 12 has a bottom wall 18, sidewalls 20extending from the bottom wall and a top wall 22. The housing 12includes a slot opening 24 in the top wall 22 and is configured topermit retraction and deployment of the airflow control member 16 intoand out of the housing 12. The active material 26 is in operativecommunication with the deployable airflow member to provide theretraction and deployment.

Using shape memory alloys as an exemplary active material, a shapememory alloy wire 26 is tethered at one end to a selected one of thewalls or stationary anchor structure 38 within the housing 12 and at theother end is tethered to the second portion 30 of the airflow controlmember 16. As shown, the deployable airflow member 16 is generally “L”shaped having a first portion 28 slidably engaged with the slot opening24 and a second portion 30 substantially perpendicular to the firstportion. The housing 12 further includes a bias spring retainingstructure 32 that is attached or integral to the top wall 22 to whichthe airflow control member 16 is slidably mounted. A bias spring 34 isdisposed intermediate and in a biased relationship with the secondportion of the airflow control member 16 and the bias spring retainingstructure 32. The bias spring retaining structure 32 further includes achannel 36 for receiving the shape memory alloy wire 26, which has oneend fixedly attached to an anchor structure 38 within the housing andthe other end and fixedly attached to the second portion 30. The shapememory alloy wire 26 is disposed about one or more pulleys 42 andthreaded through the channel 36 to provide vertical movement of theairflow control member 16. Activation of the shape memory alloy wire 26causes a phase transformation, which results in contraction of the wirewith a force sufficient to overcome those forces associated with thebias spring 34. The result is that the airflow control member 16 isslidably deployed from the slot opening 24. Deactivation causes the biasspring to psuedoplastically deform the shape memory alloy back to aboutits original position and length, which also results in retracting theairflow control member 16. In this manner, airflow as indicated byarrows 46 can be altered, which can be used to affect the downforcecaused by the airflow on the vehicle. An optional flap seal 44 isdisposed about the slot opening 24 to prevent particulate matter fromentering the housing.

For this and other embodiments disclosed herein, the bias spring isgenerally chosen so that its axial stiffness (i.e., spring constant) isgreater than that of the active material when the active material is notactivated. For example, in the case of the shape memory alloy wire, theaxial stiffness of the bias spring is chosen to be greater than that ofthe shape memory alloy wire when it is in its lower temperaturemartensite stiffness and is less than that of the wire when it is in itshigher temperature austenite phase.

In FIGS. 4 and 5, a spoiler 50 is shown in the deployed and retractedpositions, respectively. The spoiler 50 includes a housing 52 having abottom wall 54, a top wall 56, and sidewalls 58. The housing 52 furtherincludes a slot opening 60 in which an airflow control member 62 isslidably engaged therewith. The airflow control member 62 is generally“L” shaped having a first portion 64 and a second portion 66substantially perpendicular to the first portion. A bias spring 68 hasone end fixed attached to the second portion 66 and the other endfixedly attached to the bottom wall 54. An active material 70, e.g., istethered at one end to a selected one of the walls or stationary anchorstructure 72 within the housing 62 and at the other end is tethered tothe second portion 66 of the airflow control member 62. The shape memoryalloy wire 70 is disposed about one or more pulleys 74 and configured toprovide vertical movement of the airflow control member 62. Activationof the shape memory alloy wire 70 causes a phase transformation, whichresults in contraction of the wire with a force sufficient to overcomethose forces associated with the bias spring 68.

In this embodiment, activation of the shape memory alloy wire 70 wouldcause simultaneous contraction of the shape memory alloy wire andexpansion of the bias spring to deploy the airflow control member 62 asopposed to compressive process shown in previous embodiment discussedimmediately above. Deactivation of the shape memory alloy wire wouldresult in the bias spring pseudoplastically deforming the shape memoryalloy wire to retract the airflow control member within the housing 62.A seal can be disposed about the slot opening.

In FIGS. 6 and 7, a spoiler 80 is shown in the retracted and deployedpositions, respectively. The spoiler 80 includes a housing 82 having abottom wall 84, a top wall 86, and sidewalls 88. The housing 52 furtherincludes a slot opening 90 in which an airflow control member 92 isslidably engaged therewith. The slot opening 90 extends to the bottomwall and includes a shoulder 94 distally located from the top surface86. The airflow control member 92 has a generally planar shape and isslidably engaged with the slot opening.

An active material 96, e.g., shape memory alloy wire, is tethered at oneend to the airflow control member 92 and at the other end to the bottomwall 84 within the housing 82. The shape memory alloy wire 96 isconfigured to provide vertical movement of the airflow control member82. A bias spring 98 is seated onto the shoulder 94 and is in contactwith the airflow control member 92. The bias spring 98 is dimensionedsuch that in the absence of an activation signal to the shape memoryalloy wire, the bias spring positions the airflow control member 82 intothe air flow path, i.e., causes deployment of the airflow control memberfrom the housing. Upon activation of the shape memory alloy wire, thewire contracts causing the bias spring to compress, thereby retractingthe airflow control member 82. As such, the length of the slot openingto the shoulder of the recess is about equal or less than the length ofthe airflow deployable member 92 and the length of the bias spring uponcompression by the shape memory alloy wire.

In another embodiment shown in FIG. 8, a spoiler 100 is depicted inwhich the active material (one or more) is connected externally eitherdirectly or remotely to the airflow control member 102. In this example,the airflow control surface 102 is attached to a axle 104, which is freeto rotate about its axis. A spring 106 and an SMA wire 108 are attachedto the hollow tube 104 in an opposing fashion such that their tensionsbalance each other and rotation of the tube through external means willincrease the tension in one while reducing tension in the other. At lowvehicle speeds, tension in the spring 106 combined with reducedstiffness and greater length in the SMA wire 108 keeps the spoilerrotated flush to the vehicle surface and out of the way. At high vehiclespeeds, the temperature of the SMA wire is raised, e.g., throughresistance heating, to produce a phase change from martensite toaustenite in the SMA wire. This results in typically a four percentreduction in its length and a significant increase in its stiffness.This combined change in length and stiffness results in arotation—deployment—of the airflow control device and a stretching ofthe counterbalancing spring 106. Upon shutting off the current that iscausing resistance heating of the SMA wire, the wire cools to itsmartensite phase and the stretched spring returns the airflow controldevice to its stowed position.

Although reference has been made specifically to the use of shape memoryalloys, it is to be noted that an EAP could also be used in place of SMAas the actuator in these embodiments in order to achieve the desiredlinear or rotary deployment. Especially in the case of deployment bytranslation, packaging becomes much less an issue with EAP, as variouslyin tendon, sheet, or slab form, EAP can be made to experience 100%strain when subjected to an applied voltage.

Embodiments are also envisioned, as indicated, in which the externallyattached active material is used to morph the airflow control surface(s)of the spoiler. As shown in FIG. 9, the spoiler 110 includes a cam-likedevice that is located adjacent to a flexible surface of an airflowcontrol member 114. Activation of an active material 116 physicallylinked to the cam 112, such as an SMA wire or spring or an EAP sheet ortendon will cause rotation of the cam, which rotation elasticallydeforms the flexible airflow control surface of the airflow controldevice. A bias spring 118, which could take various forms, or the energystored elastically in the deformed surface could be used to return thesurface of the airflow control device to its original configuration oncethe activation signal is removed.

In an alternative embodiment, the airflow control devices can beconfigured with latching mechanisms, involving either active materialsdirectly (such as holding in position through the field activated changein shear strength in ER and MR fluids), or that are active materialactuated or otherwise, that hold the deployable airflow control devicein either the deployed or stowed positions thus allowing either power onor power off position/shape hold, i.e., in power off approaches powerfor actuation is then only needed in these embodiments during deployingor stowing of the active airflow control device.

In another embodiment, the spoiler defines a discrete body (i.e.,airflow member) positioned on, positioned above, or positioned within arecess within the vehicle surface, that by its movement/repositioningwith respect to the vehicle surface can increase or decrease airflowdown force during movement of the vehicle. As shown in FIGS. 10 and 11,the spoiler 120 is illustrated utilizing active material translatableposts 122 upon which the air deflecting member 124 is seated.

The spoiler 120 includes a spoiler body 122 (i.e., airflow controlmember) seated onto at least one post 124 (two of which are shown inFIG. 10). The post is translatable with respect the vehicle body 126. Byway of example, the post is disposed within a recess 128 formed in thevehicle body. However, it should be noted that the posts may bevariously slidably engaged with slot opening in the airflow controlmember, the vehicle surface, or both and/or contain telescoping portionsthat can extend or shorten their height. An active material actuatorsimilar to those discussed above comprising an active material isdisposed in operative communication with the airflow control member toeffect raising, lowering, and/or rotating of the airflow control memberwith respect to the vehicle surface. A latch 130 may be employed to lockthe airflow member 122 at a desired position, e.g., in the fullydeployed or retracted positions, which then permits deactivation of theactive material while maintaining the position of the airflow controlmember.

FIG. 12 illustrates an exemplary active material actuator 140 thatretracts the post 124 when the active material is activated. The post124 is seated on a compression spring 142. An active material such as ashape memory alloy wire is anchored to the spoiler at one end 146 and tothe vehicle 126 at another end 148. One or more pulleys 150 can beutilized to configure the active material actuator 140. The post 124moves downward and is latched upon activation of the active material 144as shown. Upon deactivation, the latch can be selectively unlatchedcausing the compression spring to decompress and deploy the post andairflow member 122 from the vehicle body. In the case of shape memoryalloys, the wire would pseudoplastically deform.

FIG. 13 illustrates an exemplary active material actuator 160 thatdeploys the post when the active material is activated. In thisembodiment, a compression spring 162 is biased such that the post 124 isin the retracted position when the active material (counterforce) is notactivated. Upon activation of the active material 166, the post deploysfrom the vehicle body. Using shape memory alloys as an exemplary activematerial, one end of the SMA is anchored to the vehicle at anchor point168 and at its other end to the post 124 at anchor point 170.Optionally, a pulley 164 can be employed. A latch 130 can be used toselectively maintain the spoiler in an “up” position even when theactive material is deactivated. The latch can be integrated with theactive material actuator (i.e., be active material actuated),mechanically actuated, hydraulically actuated, or pneumatically actuatedas may be desired for different applications. In a preferred embodiment,the actuator wires are horizontally disposed within the length of thespoiler or within the vehicle body.

Active material includes those compositions that can exhibit a change instiffness properties, shape and/or dimensions in response to theactivation signal, which can take the type for different activematerials, of electrical, magnetic, thermal and like fields. Preferredactive materials include but are not limited to the class of shapememory materials, and combinations thereof. Shape memory materialsgenerally refer to materials or compositions that have the ability toremember their original at least one attribute such as shape, which cansubsequently be recalled by applying an external stimulus, as will bediscussed in detail herein. As such, deformation from the original shapeis a temporary condition. In this manner, shape memory materials canchange to the trained shape in response to an activation signal.

Generally, SMPs are phase segregated co-polymers comprising at least twodifferent units, which may be described as defining different segmentswithin the SMP, each segment contributing differently to the overallproperties of the SMP. As used herein, the term “segment” refers to ablock, graft, or sequence of the same or similar monomer or oligomerunits, which are copolymerized to form the SMP. Each segment may becrystalline or amorphous and will have a corresponding melting point orglass transition temperature (Tg), respectively. The term “thermaltransition temperature” is used herein for convenience to genericallyrefer to either a Tg or a melting point depending on whether the segmentis an amorphous segment or a crystalline segment. For SMPs comprising(n) segments, the SMP is said to have a hard segment and (n−1) softsegments, wherein the hard segment has a higher thermal transitiontemperature than any soft segment. Thus, the SMP has (n) thermaltransition temperatures. The thermal transition temperature of the hardsegment is termed the “last transition temperature”, and the lowestthermal transition temperature of the so-called “softest” segment istermed the “first transition temperature”. It is important to note thatif the SMP has multiple segments characterized by the same thermaltransition temperature, which is also the last transition temperature,then the SMP is said to have multiple hard segments.

When the SMP is heated above the last transition temperature, the SMPmaterial can be shaped. A permanent shape for the SMP can be set ormemorized by subsequently cooling the SMP below that temperature. Asused herein, the terms “original shape”, “previously defined shape”, and“permanent shape” are synonymous and intended to be usedinterchangeably. A temporary shape can be set by heating the material toa temperature higher than a thermal transition temperature of any softsegment yet below the last transition temperature, applying an externalstress or load to deform the SMP, and then cooling below the particularthermal transition temperature of the soft segment.

The permanent shape can be recovered by heating the material, with thestress or load removed, above the particular thermal transitiontemperature of the soft segment yet below the last transitiontemperature. Thus, it should be clear that by combining multiple softsegments it is possible to demonstrate multiple temporary shapes andwith multiple hard segments it may be possible to demonstrate multiplepermanent shapes. Similarly using a layered or composite approach, acombination of multiple SMPs will demonstrate transitions betweenmultiple temporary and permanent shapes.

For SMPs with only two segments, the temporary shape of the shape memorypolymer is set at the first transition temperature, followed by coolingof the SMP, while under load, to lock in the temporary shape. Thetemporary shape is maintained as long as the SMP remains below the firsttransition temperature. The permanent shape is regained when the SMP isonce again brought above the first transition temperature. Repeating theheating, shaping, and cooling steps can repeatedly reset the temporaryshape.

Most SMPs exhibit a “one-way” effect, wherein the SMP exhibits onepermanent shape. Upon heating the shape memory polymer above a softsegment thermal transition temperature without a stress or load, thepermanent shape is achieved and the shape will not revert back to thetemporary shape without the use of outside forces.

As an alternative, some shape memory polymer compositions can beprepared to exhibit a “two-way” effect, wherein the SMP exhibits twopermanent shapes. These systems include at least two polymer components.For example, one component could be a first cross-linked polymer whilethe other component is a different cross-linked polymer. The componentsare combined by layer techniques, or are interpenetrating networks,wherein the two polymer components are cross-linked but not to eachother. By changing the temperature, the shape memory polymer changes itsshape in the direction of a first permanent shape or a second permanentshape. Each of the permanent shapes belongs to one component of the SMP.The temperature dependence of the overall shape is caused by the factthat the mechanical properties of one component (“component A”) arealmost independent from the temperature in the temperature interval ofinterest. The mechanical properties of the other component (“componentB”) are temperature dependent in the temperature interval of interest.In one embodiment, component B becomes stronger at low temperaturescompared to component A, while component A is stronger at hightemperatures and determines the actual shape. A two-way memory devicecan be prepared by setting the permanent shape of component A (“firstpermanent shape”), deforming the device into the permanent shape ofcomponent B (“second permanent shape”), and fixing the permanent shapeof component B while applying a stress.

It should be recognized by one of ordinary skill in the art that it ispossible to configure SMPs in many different forms and shapes.Engineering the composition and structure of the polymer itself canallow for the choice of a particular temperature for a desiredapplication. For example, depending on the particular application, thelast transition temperature may be about 0° C. to about 300° C. orabove. A temperature for shape recovery (i.e., a soft segment thermaltransition temperature) may be greater than or equal to about −30° C.Another temperature for shape recovery may be greater than or equal toabout 20° C. Another temperature for shape recovery may be greater thanor equal to about 70° C. Another temperature for shape recovery may beless than or equal to about 250° C. Yet another temperature for shaperecovery may be less than or equal to about 200° C. Finally, anothertemperature for shape recovery may be less than or equal to about 180°C.

Suitable polymers for use in the SMPs include thermoplastics,thermosets, interpenetrating networks, semi-interpenetrating networks,or mixed networks of polymers. The polymers can be a single polymer or ablend of polymers. The polymers can be linear or branched thermoplasticelastomers with side chains or dendritic structural elements. Suitablepolymer components to form a shape memory polymer include, but are notlimited to, polyphosphazenes, poly(vinyl alcohols), polyamides,polyester amides, poly(amino acid)s, polyanhydrides, polycarbonates,polyacrylates, polyalkylenes, polyacrylamides, polyalkylene glycols,polyalkylene oxides, polyalkylene terephthalates, polyortho esters,polyvinyl ethers, polyvinyl esters, polyvinyl halides, polyesters,polylactides, polyglycolides, polysiloxanes, polyurethanes, polyethers,polyether amides, polyether esters, polystyrene, polypropylene,polyvinyl phenol, polyvinylpyrrolidone, chlorinated polybutylene,poly(octadecyl vinyl ether) ethylene vinyl acetate, polyethylene,poly(ethylene oxide)-poly(ethylene terephthalate), polyethylene/nylon(graft copolymer), polycaprolactones-polyamide (block copolymer),poly(caprolactone) dimethacrylate-n-butyl acrylate,poly(norbornyl-polyhedral oligomeric silsesquioxane), polyvinylchloride, urethane/butadiene copolymers, polyurethane block copolymers,styrene-butadiene-styrene block copolymers, and the like, andcombinations comprising at least one of the foregoing polymercomponents. Examples of suitable polyacrylates include poly(methylmethacrylate), poly(ethyl methacrylate), poly(butyl methacrylate),poly(isobutyl methacrylate), poly(hexyl methacrylate), poly(isodecylmethacrylate), poly(lauryl methacrylate), poly(phenyl methacrylate),poly(methyl acrylate), poly(isopropyl acrylate), poly(isobutyl acrylate)and poly(octadecyl acrylate). The polymer(s) used to form the varioussegments in the SMPs described above are either commercially availableor can be synthesized using routine chemistry. Those of skill in the artcan readily prepare the polymers using known chemistry and processingtechniques without undue experimentation.

Similar to shape memory polymers, shape memory alloys exist in severaldifferent temperature-dependent phases. The most commonly utilized ofthese phases are the so-called martensite and austenite phases. In thefollowing discussion, the martensite phase generally refers to the moredeformable, lower temperature phase whereas the austenite phasegenerally refers to the more rigid, higher temperature phase. When theshape memory alloy is in the martensite phase and is heated, it beginsto change into the austenite phase. The temperature at which thisphenomenon starts is often referred to as austenite start temperature(As). The temperature at which this phenomenon is complete is called theaustenite finish temperature (Af). When the shape memory alloy is in theaustenite phase and is cooled, it begins to change into the martensitephase, and the temperature at which this phenomenon starts is referredto as the martensite start temperature (Ms). The temperature at whichaustenite finishes transforming to martensite is called the martensitefinish temperature (Mf). Generally, the shape memory alloys are softerand more easily deformable in their martensitic phase and are harder,stiffer, and/or more rigid in the austenitic phase. In view of theforegoing properties, expansion of the shape memory alloy is preferablyat or below the austenite transition temperature (at or below As).Subsequent heating above the austenite transition temperature causes theexpanded shape memory alloy to revert back to its permanent shape. Thus,a suitable activation signal for use with shape memory alloys is athermal activation signal having a magnitude to cause transformationsbetween the martensite and austenite phases.

The temperature at which the shape memory alloy remembers its hightemperature form when heated can be adjusted by slight changes in thecomposition of the alloy and through heat treatment. In nickel-titaniumshape memory alloys, for instance, it can be changed from above about100° C. to below about −100° C. The shape recovery process occurs over arange of just a few degrees and the start or finish of thetransformation can be controlled to within a degree or two depending onthe desired application and alloy composition. The mechanical propertiesof the shape memory alloy vary greatly over the temperature rangespanning their transformation, typically providing shape memory effects,superelastic effects, and high damping capacity.

Suitable shape memory alloy materials include, but are not intended tobe limited to, nickel-titanium based alloys, indium-titanium basedalloys, nickel-aluminum based alloys, nickel-gallium based alloys,copper based alloys (e.g., copper-zinc alloys, copper-aluminum alloys,copper-gold, and copper-tin alloys), gold-cadmium based alloys,silver-cadmium based alloys, indium-cadmium based alloys,manganese-copper based alloys, iron-platinum based alloys,iron-palladium based alloys, and the like. The alloys can be binary,ternary, or any higher order so long as the alloy composition exhibits ashape memory effect, e.g., change in shape orientation, changes in yieldstrength, and/or flexural modulus properties, damping capacity,superelasticity, and the like. Selection of a suitable shape memoryalloy composition depends on the temperature range where the componentwill operate.

Active materials also include, but are not limited to, shape memorymaterial such as magnetic materials and magnetorheological elastomers.Suitable magnetic materials include, but are not intended to be limitedto, soft or hard magnets; hematite; magnetite; magnetic material basedon iron, nickel, and cobalt, alloys of the foregoing, or combinationscomprising at least one of the foregoing, and the like. Alloys of iron,nickel and/or cobalt, can comprise aluminum, silicon, cobalt, nickel,vanadium, molybdenum, chromium, tungsten, manganese and/or copper.Suitable MR elastomer materials have previously been described.

The spoilers and methods of the present disclosure are able to adjustfeatures such as shape, dimension, stiffness, location, combinationsthereof, and the like by changing the at least one attribute of activematerial to match the needs of different driving conditions. Changes inat least one attribute of active material include shape, dimension,stiffness, combinations thereof and the like. Utilizing active materialsto affect these changes provide devices of increased simplicity androbustness, while reducing the number of failure modes, device volumeand energy requirements for activation due to higher energy densities.

The active material may also comprise an electroactive polymer such asionic polymer metal composites, conductive polymers, piezoelectricmaterial and the like. As used herein, the term “piezoelectric” is usedto describe a material that mechanically deforms when a voltagepotential is applied, or conversely, generates an electrical charge whenmechanically deformed.

Suitable MR elastomer materials include, but are not intended to belimited to, an elastic polymer matrix comprising a suspension offerromagnetic or paramagnetic particles, wherein the particles aredescribed above. Suitable polymer matrices include, but are not limitedto, poly-alpha-olefins, natural rubber, silicone, polybutadiene,polyethylene, polyisoprene, and the like.

Electroactive polymers include those polymeric materials that exhibitpiezoelectric, pyroelectric, or electrostrictive properties in responseto electrical or mechanical fields. The materials generally employ theuse of compliant electrodes that enable polymer films to expand orcontract in the in-plane directions in response to applied electricfields or mechanical stresses. An example of an electrostrictive-graftedelastomer with a piezoelectric poly(vinylidenefluoride-trifluoro-ethylene) copolymer. This combination has the abilityto produce a varied amount of ferroelectric-electrostrictive molecularcomposite systems. These may be operated as a piezoelectric sensor oreven an electrostrictive actuator.

Materials suitable for use as an electroactive polymer may include anysubstantially insulating polymer or rubber (or combination thereof) thatdeforms in response to an electrostatic force or whose deformationresults in a change in electric field. Exemplary materials suitable foruse as a pre-strained polymer include silicone elastomers, acrylicelastomers, polyurethanes, thermoplastic elastomers, copolymerscomprising PVDF, pressure-sensitive adhesives, fluoroelastomers,polymers comprising silicone and acrylic moieties, and the like.Polymers comprising silicone and acrylic moieties may include copolymerscomprising silicone and acrylic moieties, polymer blends comprising asilicone elastomer and an acrylic elastomer, for example.

Materials used as an electroactive polymer may be selected based on oneor more material properties such as a high electrical breakdownstrength, a low modulus of elasticity (for large or small deformations),a high dielectric constant, and the like. In one embodiment, the polymeris selected such that is has an elastic modulus at most about 100 MPa.In another embodiment, the polymer is selected such that is has amaximum actuation pressure between about 0.05 MPa and about 10 MPa, andpreferably between about 0.3 MPa and about 3 MPa. In another embodiment,the polymer is selected such that is has a dielectric constant betweenabout 2 and about 20, and preferably between about 2.5 and about 12. Thepresent disclosure is not intended to be limited to these ranges.Ideally, materials with a higher dielectric constant than the rangesgiven above would be desirable if the materials had both a highdielectric constant and a high dielectric strength. In many cases,electroactive polymers may be fabricated and implemented as thin films.Thicknesses suitable for these thin films may be below 50 micrometers.

As electroactive polymers may deflect at high strains, electrodesattached to the polymers should also deflect without compromisingmechanical or electrical performance. Generally, electrodes suitable foruse may be of any shape and material provided that they are able tosupply a suitable voltage to, or receive a suitable voltage from, anelectroactive polymer. The voltage may be either constant or varyingover time. In one embodiment, the electrodes adhere to a surface of thepolymer. Electrodes adhering to the polymer are preferably compliant andconform to the changing shape of the polymer. Correspondingly, thepresent disclosure may include compliant electrodes that conform to theshape of an electroactive polymer to which they are attached. Theelectrodes may be only applied to a portion of an electroactive polymerand define an active area according to their geometry. Various types ofelectrodes suitable for use with the present disclosure includestructured electrodes comprising metal traces and charge distributionlayers, textured electrodes comprising varying out of plane dimensions,conductive greases such as carbon greases or silver greases, colloidalsuspensions, high aspect ratio conductive materials such as carbonfibrils and carbon nanotubes, and mixtures of ionically conductivematerials.

Materials used for electrodes of the present disclosure may vary.Suitable materials used in an electrode may include graphite, carbonblack, colloidal suspensions, thin metals including silver and gold,silver filled and carbon filled gels and polymers, and ionically orelectronically conductive polymers. It is understood that certainelectrode materials may work well with particular polymers and may notwork as well for others. By way of example, carbon fibrils work wellwith acrylic elastomer polymers while not as well with siliconepolymers.

The active material may also comprise a piezoelectric material. Also, incertain embodiments, the piezoelectric material may be configured as anactuator for providing rapid deployment. As used herein, the term“piezoelectric” is used to describe a material that mechanically deforms(changes shape) when a voltage potential is applied, or conversely,generates an electrical charge when mechanically deformed. Preferably, apiezoelectric material is disposed on strips of a flexible metal orceramic sheet. The strips can be unimorph or bimorph. Preferably, thestrips are bimorph, because bimorphs generally exhibit more displacementthan unimorphs.

One type of unimorph is a structure composed of a single piezoelectricelement externally bonded to a flexible metal foil or strip, which isstimulated by the piezoelectric element when activated with a changingvoltage and results in an axial buckling or deflection as it opposes themovement of the piezoelectric element. The actuator movement for aunimorph can be by contraction or expansion. Unimorphs can exhibit astrain of as high as about 10%, but generally can only sustain low loadsrelative to the overall dimensions of the unimorph structure.

In contrast to the unimorph piezoelectric device, a bimorph deviceincludes an intermediate flexible metal foil sandwiched between twopiezoelectric elements. Bimorphs exhibit more displacement thanunimorphs because under the applied voltage one ceramic element willcontract while the other expands. Bimorphs can exhibit strains up toabout 20%, but similar to unimorphs, generally cannot sustain high loadsrelative to the overall dimensions of the unimorph structure.

Suitable piezoelectric materials include inorganic compounds, organiccompounds, and metals. With regard to organic materials, all of thepolymeric materials with non-centrosymmetric structure and large dipolemoment group(s) on the main chain or on the side-chain, or on bothchains within the molecules, can be used as candidates for thepiezoelectric film. Examples of suitable polymers include, for example,but are not limited to, poly(sodium 4-styrenesulfonate) (“PSS”), polyS-119 (poly(vinylamine)backbone azo chromophore), and their derivatives;polyfluorocarbons, including polyvinylidene fluoride (“PVDF”), itsco-polymer vinylidene fluoride (“VDF”), trifluoroethylene (TrFE), andtheir derivatives; polychlorocarbons, including poly(vinyl chloride)(“PVC”), polyvinylidene chloride (“PVC2”), and their derivatives;polyacrylonitriles (“PAN”), and their derivatives; polycarboxylic acids,including poly(methacrylic acid (“PMA”), and their derivatives;polyureas, and their derivatives; polyurethanes (“PUE”), and theirderivatives; bio-polymer molecules such as poly-L-lactic acids and theirderivatives, and membrane proteins, as well as phosphate bio-molecules;polyanilines and their derivatives, and all of the derivatives oftetramines; polyimides, including Kapton molecules and polyetherimide(“PEI”), and their derivatives; all of the membrane polymers;poly(N-vinyl pyrrolidone) (“PVP”) homopolymer, and its derivatives, andrandom PVP-co-vinyl acetate (“PVAc”) copolymers; and all of the aromaticpolymers with dipole moment groups in the main-chain or side-chains, orin both the main-chain and the side-chains, and mixtures thereof.

Further, piezoelectric materials can include Pt, Pd, Ni, Ti, Cr, Fe, Ag,Au, Cu, and metal alloys and mixtures thereof. These piezoelectricmaterials can also include, for example, metal oxide such as SiO₂,Al₂O₃, ZrO₂, TiO₂, SrTiO₃, PbTiO₃, BaTiO₃, FeO₃, Fe₃O₄, ZnO, andmixtures thereof; and Group VIA and IIB compounds, such as CdSe, CdS,GaAs, AgCaSe₂, ZnSe, GaP, InP, ZnS, and mixtures thereof.

Suitable active materials also comprise magnetorheological (MR)compositions, such as MR elastomers, which are known as “smart”materials whose rheological properties can rapidly change uponapplication of a magnetic field. MR elastomers are suspensions ofmicrometer-sized, magnetically polarizable particles in a thermosetelastic polymer or rubber. The stiffness of the elastomer structure isaccomplished by changing the shear and compression/tension moduli byvarying the strength of the applied magnetic field. The MR elastomerstypically develop structure when exposed to a magnetic field in aslittle as a few milliseconds. Discontinuing the exposure of the MRelastomers to the magnetic field reverses the process and the elastomerreturns to its lower modulus state.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about”. Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe following specification and attached claims are approximations thatmay vary depending upon the desired properties sought to be obtained bythe present disclosure. At the very least, and not as an attempt tolimit the application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques.

While the disclosure has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the disclosure. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the disclosure without departing fromthe essential scope thereof. Therefore, it is intended that thedisclosure not be limited to the particular embodiment disclosed as thebest mode contemplated for carrying out this disclosure, but that thedisclosure will include all embodiments falling within the scope of theappended claims.

1. A spoiler adapted for use with a vehicle, such that the spoilerdefines a surface of the vehicle that can increase or decrease airflowdownforce during movement of the vehicle, the spoiler comprising: ahousing having an opening; an airflow control member translatablydisposed within the housing and slidably engaged with the opening; anactuator comprising an active material in operative communication withthe member, operable to undergo a reversible change when exposed to oroccluded from an activation signal, and configured to exert atranslation force upon, so as to effect deployment or retraction of themember from or into the housing; and a biasing element disposed withinthe housing, and configured to exert a linear biasing force upon themember antagonistically to and less than the translation force.
 2. Thespoiler of claim 1, wherein the active material is selected from a groupconsisting of shape memory alloys, shape memory polymers, electroactivepolymers, ferromagnetic shape memory alloys, electrorheological fluids,magnetorheological fluids, dielectric elastomers, ionic polymer metalcomposites, piezoelectric polymers, and piezoelectric ceramics.
 3. Thespoiler of claim 1, wherein the active material actuator comprises ashape memory alloy wire having one end linked to the airflow controlmember and a bias spring attached to the airflow control memberconfigured to provide a counter force to that provided by the shapememory alloy wire.
 4. The spoiler of claim 3, wherein the bias springhas a spring constant greater than the force exerted upon the member bythe shape memory alloy wire when the shape memory alloy wire is in amartensite phase and less than the translation force.
 5. The spoiler ofclaim 1, further comprising a flap seal disposed about the opening, theflap seal configured to prevent particulate matter from entering thehousing.
 6. The spoiler of claim 3, further comprising at least onepulley in operative communication with the shape memory alloy wire. 7.The spoiler of claim 3, wherein the housing comprises a top wall, abottom wall and sidewalls extending therebetween, wherein the top wallcomprises a bias spring retaining structure within the housing, whereinthe airflow control member comprises a first portion in slidingengagement with the opening and a second portion with the bias springintermediate the bias spring retaining structure and the second portion,and wherein the shape memory alloy wire is configured to contract andcompress the bias spring upon activation and extend the first portionfrom the housing.
 8. The spoiler of claim 7, wherein the bias spring isconfigured to expand and retract the first portion into the housing whenthe shape memory alloy wire is not activated.
 9. The spoiler of claim 3,wherein the housing comprises a top wall, a bottom wall and sidewallsextending therebetween, wherein the airflow control member comprises afirst portion in sliding engagement with the opening and a secondportion with the bias spring intermediate the bottom wall and the secondportion, and wherein the shape memory alloy wire is configured tocontract and expand the bias spring upon activation and extend the firstportion from the housing.
 10. The spoiler of claim 9, wherein the biasspring is configured to compress and retract the first portion into thehousing when the shape memory alloy wire is not activated.
 11. Thespoiler of claim 3, wherein the airflow control member has asubstantially linear shape orientation that is in sliding engagementwith the opening, wherein the bias spring is seated on a shoulder of theopening and is intermediate the airflow control member and the shoulder,and wherein the shape memory alloy wire is configured to contract andcompress the bias spring upon activation and retract the airflow controlmember from the housing.
 12. The spoiler of claim 11, wherein the biasspring is configured to expand and deploy the airflow control memberfrom the housing when the shape memory alloy wire is not activated.